Life on earth largely depends on the conversion of light energy into chemical energy through photosynthesis by plants. However, absorption of excess sunlight can damage the complex machinery responsible for this process. Researchers from the University of Geneva (UNIGE), Switzerland, have discovered how Chlamydomonas reinhardtii, a mobile single-cell alga, activates the protection of its photosynthetic machinery. Their study, published in the journal PNAS, indicates that the receptors (UVR8) that detect ultraviolet rays induce the activation of a safety valve that allows dissipation of excess energy as heat. A second protective role is thus attributed to these receptors, whose ability to induce the production of an anti-UV ‘sunscreen’ had already been shown by the Geneva team.